TM 9-2910-226-34 (3) Refer to figure 3-121. Position compressor and secure with two stud sleeves (A) and hydraulic head nuts (B). Turn thumb screw (C) clockwise to compress plunger spring seat. Install spring retaining ring (D) using suitable pliers. Release spring tension by turning thumb screw coun- terclockwise and remove the compressor. Figure 3-121. Installing tappet spring retaining ring using compressor. 3-40. Installation of Hydraulic Head Assembly. NOTE For proper selection of hydraulic head assemblies refer to table 3-2. a. Assembly. The hydraulic head was inspected and assembled during repair (para 3-28). b. Installation. CAUTION Do not force the hydraulic head into the housing. A slight pressure will be required to seat the preformed packings in the housing. (1) Refer to figure 3-122. Position hydraulic head assembly (A) on injection pump housing so plunger sleeve slot faces opening, and aline slotted tooth of plunger drive gear with arrow on injection pump housing. Install four stud sleeves (B) and hydraulic head nuts (C). Torque tighten nuts to 18- 20 foot-pounds. Figure 3-122. Installing hydraulic head assembly. NOTE Sub-paragraphs (2), (3), and (4) below apply to code F and G pumps only. (2) Refer to figure 3-123. Install filter screw copper gasket (A) and oil filter (B) on filter screw (D). Apply grease, Federal specification VV-P-236, to filter screw packing (C), and install on oil filter screw (D). Install oil filter screw and associated parts. Torque tighten screw to 20-25 foot-pounds. Figure 3-123. Installing oil filter. 3-74